Relating to texturizing vegetable protein, many methods have heretofore been known. For example, there is the spinning method in which an alkaline solution of protein is forcibly extruded through an orifice, and caused to be solidified in a bath containing a coagulant thereby making it to be fibrous. This method is superior in removal of the bad smell inherent in the raw material and in conversion to the desired fibrous structure, however it requires several chemicals for the process and complicated processing, and therefore it can not be said to be an economical method. As the method best known in the art, there is the so-called extruding method. This is a method wherein a protein raw material, heated at a high temperature and under pressure is discharged, thereby resulting in an expanded and texturized product. Many improvements of this method have been developed. This method has an advantage that its process is simple and allows the production of textured vegetable protein at a lower price. However, relating to the quality of products, there are still present the difficulties that most of bad smell inherent in the raw material remains and there is a lack of the desired fibrous textures.
Moreover, recently there has been developed a method of making a reticulated textured structure by use of steam. For example, Japanese Patent Application Laying-Open No. 15853/77 discloses such a method that in a treating area the protein is caused to be texturized by steam. This method is superior to the extruding method in quality and also to the spinning method in economy. However, the product has such a minute reticulated structure that it can be recognized only by microscopic examination, but it appears to be particle-like by observation with the naked eye, and therefore the use of the product is limited. Furthermore, there is known a method of Japanese Patent Application Publication No. 6665/74 in which the protein is texturized by making the protein in an aqueous liquid directly contact steam, but although this product also has such a reticulated structure as recognized only by microscopic examination, it is also one that has been broken into small pieces by the steam current. This steaming method is also insufficient in deodorization.
Moreover, the study by Saio et al. reported in J. Food Sci. 39 777 (1974) is one in which soybean protein is coagulated by calcium salt or acid to produce a curd, which is then dehydrated to make an aggregate, and this aggregate is introduced into water or a buffer solution and then put into an autoclave as it is and heated at a temperature above 100.degree. C. This method requires a plurality of processes for causing the protein to be texturized, so that it can not be said to be an economical method, and also the resulting product has a porous structure like "Aburaage" (fried curd of soybean protein) or "Koridofu" (dried curd of soybean protein).